Custom Nodes Variables Not Being Stored
You need to define it outside of the functions to make it a property of the class. Try adding something like the following before your 'def's :
class Test_Node(Node, Base_Node):
    bl_label = &quot;Test Node&quot;
    
    #Define class-level property
    Test_Bool: bpy.props.BoolProperty() 

    def init(self, context):
        .....etc.

This will define a new class-level property 'Test_Bool' and this should then be available as 'self.Test_Bool' from any of the functions within the class.